Mild cognitive impairment is defined as an intermediate state between normal cognitive function and dementia. In addition to neurodegenerative diseases, vascular insults, trauma, and drugs can induce this condition. Mild cognitive decline reported by patients themselves or during history taking is the principal diagnostic criteria. Patients are distinguished from those suffering from dementia by their ability to live independently and perform daily activities without assistance or with minor assistance.
The diagnostic criteria for mild cognitive impairment (MCI) have undergone several revisions in recent years but this clinical entity is generally known as an intermediate state between normal cognitive impairment and dementia  . More specifically, MCI is suspected if the cognitive decline is acquired unexpectedly sooner in terms of age or educational background, but without the impairment of activities of daily living  . Patients can experience a decline in one of the five cognitive domains: language; executive functioning; psychomotor skills; learning and memory; or visuospatial abilities  . The distinction between dementia and MCI lies in the fact that the majority of patients suffering from MCI have only one (or sometimes more than one) cognitive deficits, e.g. memory complaints, whereas dementia is usually characterized by multiple cognitive deficits . Furthermore, MCI is distinguished by the preservation of functional independence and activities of daily living, although time to complete more complex tasks, such as cooking, shopping or paying bills may be increased and is often noted by patients themselves . The objectivity and self-awareness of patients about their cognitive decline are also the key criteria for MCI   . This disorder most frequently arises in the setting of Alzheimer's disease and other forms of dementia (Parkinson's disease, and less commonly frontotemporal degeneration), which is why the lifetime risk for full-blown dementia is substantially increased in this patient population  . However, cerebrovascular diseases, traumatic brain injury, depression and multiple comorbidities have also been implicated in the pathogenesis of MCI  . In any case, prompt recognition is mandatory in order to ensure the best possible outcome.
A meticulous patient history is the most important step in the workup for diagnosing MCI. During the interview, patients should be asked about their daily routine and whether certain activities have become more complex for them to perform. A heterogeneous anamnesis (with either family members or close friends) may provide useful clues, but the hallmark of MCI is self-reported cognitive decline, which can only be revealed during history taking and a full cognitive examination  . It must be kept in mind that many drugs also induce cognitive impairment, which is why a recent history of drug use should be investigated . To confirm MCI, several inventories can be used, one example being the 10-item functional activities questionnaire, which establishes if patients had difficulties with activities of various complexity (remembering appointments, driving, traveling, sorting out bills, cooking, etc.)  . In addition, the mental status needs to be evaluated, either by using the Montreal Cognitive Assessment (MOCA) or the Short Test of Mental Status (STMS), which seems to be superior compared to the Mini-Mental State Examination (MMSE), one of the most widely implemented cognitive assessments  . A complete neurological exam is an integral part of the workup in all patients in whom MCI and other neurological disorders are suspected, especially if other etiologies (e.g. cerebrovascular disease) are the cause of the symptoms. Also for this reason, imaging studies - computed tomography (CT) or magnetic resonance imaging (MRI) are mandatory during the workup.